Patients with sickle cell disease at Duke and UNC are screened for proteinuria and hyperfiltration. Biopsies are done on those with significant proteinuria. Patients are also encouraged to enroll in the CRU inpatient study of renal function and the effect of Enalapril. The goal is to define the earliest lesions and to determine whether inhibition of efferent arteriolar vaso-constriction improves proteinuria and/or renal function.